Study On Synthesis Of Amphoteric Starch QAP And It's Application

Starch is one of the most abundant natural polymers in the earth. Amphoteric starch is a kind of natural polysaccharide source, which has import value in various areas. In recent ten years, the application of amphoteric polymer has been stressed and studied. In water treatment it was also reported that amphoteric polymer flocculants were used as adsorption agents for metal ions, decolorization agents for dye wastewater and conditioners for sludge dewatering.The thesis includes two aspects mainly: the preparation of amphoteric starch and application of amphoteric starch as flocculants in treating dyeing wastewater and house wastewater.In my research, a new kind of amphoteric polymer come from natural raw material core starch was studied: Firstly, corn starch was modified by cation reaction, and esteration reaction to obtain QAP. We choice starch as raw materials and carry out cation experiments using starch and ether-agent. The result of experiments is that a kind of high-DS cation starch was preparated successfully. During the processing of cation of starch, mole ratio of ether-agent to starch, mole ratio of alkali to ether-agent starch, concentration of H2O, reaction temperature and reaction time are primary parameters. By control of cation, we can get cation starch with different degree of substitute. In terms of cross-test design we got the condition under which the starch with high-DS.can be obtained.Secondly, On the base of this kind of cation starch, through importing anion we can get a kind of amphoteric starch QAP which ratio of anion to cation is 1 to 2.The flocculants properties of this kind of amphoteric starch in treating muddy water and dyeing waste-water were studied, and the experimental results showed that the flocculating performance of this amphoteric starch (R=0.5) is satisfactory. According to the flocculating results of QAP in treating suspension, the optimal reaction conditions were determined: phosphate/cation starch (mole ratio)= 1.94-2.02/1; reaction temperature=145-155C reaction time=3-3.5h. The amphoteric molecular structure of QAP was characterized by IR. The experimental results of solution characters and physical and chemical properties illustrated that QAP has good property of resisting salt effect and storing stability.The flocculating performance of this amphoteric starch in treating dyeing wastewater and house wastewater were studied, and the experimental results showed that the flocculating performance of amphoteric starch is satisfactory; Fading color is obvious; the rate of penetration light increases remarkably; the removal rate of COD is high, but the optimum and the optimum adding dosage should be determined previously. Owing to the cost of amphoteric starch, the use with other flocculants-PAC as compound coagulant is preferred to treat wastewater.The results showed that the effect of compound coagulant is remarkably stronger than those of communicable flocculants used singly.The last chapter of the thesis includes two aspects mainly: the principle of discolors on dye wastewater and theory of getting red of muddy water was research carefully. This part has been reported abroad, but little in china.As a natural macromolecule, ampheric starch has no poison and no harm to human body, besides it has no second pollution to environment and can be widely applied in many fields. From the viewpoint of environmental protection, amphoteric starch will become more and more useful in our country.